1. Field of the Invention
The present invention relates to endoscopic biopsy forceps devices. In particular, the invention relates to biopsy forceps jaws having a shielding structure which enshrouds the sharp edges of the teeth of the jaws when the teeth of the jaws are in a closed position.
2. State of the Art
Endoscopic biopsy forceps are used for taking tissue samples from the human body for analysis. These forceps typically have a pair of cupped jaws attached to the distal end of a long flexible coil, the proximal end of which is attached to actuating means which opens and closes the jaws when the actuating means is manipulated by the practitioner. The endoscopic biopsy procedure is accomplished through an endoscope which is inserted into a body and guided by manipulation to the biopsy site. The endoscope typically includes a long narrow flexible tube carrying distal optical means and having a narrow lumen for receiving the biopsy forceps. The practitioner guides the endoscope to the biopsy site using the optical means and inserts the forceps, with jaws closed, through the lumen of the endoscope to the biopsy site. While viewing the biopsy site through the optical means of the endoscope, the practitioner opens the forceps jaws and carefully guides the jaws around a tissue to be sampled. When the jaws are in the correct position, the practitioner manipulates the actuating means and closes the jaws on the tissue to be sampled. The cupped jaws grip the tissue and enclose a sample of the tissue in the space between the cupped jaws. The forceps are then withdrawn from the lumen of the endoscope while the jaws are kept shut, with the sample captured in the space between the cupped jaws typically torn away from the tissue at the biopsy site.
The endoscopic biopsy procedure poses several challenges to the design and manufacture of biopsy forceps and particularly biopsy forceps jaws. The jaws must be small enough to fit through the narrow lumen of the endoscope, yet strong enough and sharp enough to cut and/or tear tissue. An early example of an endoscopic biopsy forceps is shown in U.S. Pat. No. 3,895,636 to Schmidt. The forceps in Schmidt include a pair of cupped toothless jaws with sharpened opposed edges intended to cut through tissue being sampled. Due to the miniature size of the jaws, however, it is difficult to sharpen the edges to a very high degree. Consequently, it is necessary to apply great force to the jaws in order to sever the tissue being sampled. In practice, sufficient force to sever the tissue is rarely achieved. Thus, either the jaws effect a clamping action which permits the tissue to be torn away from the biopsy site, or the jaws simply slip off the tissue without cutting or tearing it.
U.S. Pat. No. 4,880,015 to Neirman shows endoscopic biopsy forceps having opposed rectangularly cupped jaws with teeth on their parallel edges. When the jaws close, opposed teeth interleave providing a slightly better gripping ability than the jaws disclosed by Schmidt. However, the rectangular configuration of the jaws and the absence of teeth at the distal end of the jaws limits their functionality. Additionally, with these jaws and other toothed jaws, the teeth often do not align properly and prevent the jaws from closing completely which adds to the inefficiency of cutting and/or tearing. Similarly, the misalignment of the opposed teeth sometimes causes the jaws to lock in the closed position.
Co-owned U.S. Pat. No. 5,228,451 to Bales et al., the complete disclosure of which is hereby incorporated by reference herein, discloses endoscopic biopsy forceps having a pair of opposed jaws with teeth which extend along the entire opposed edge of each jaw. The teeth are offset by one-half pitch so that the upper jaw and lower jaw can be made from the same mold and still allow the teeth to align (interleave) when the jaws are closed. This arrangement of jaw teeth greatly improves the cutting and/or gripping (tearing) action of the forceps. It is a perceived problem, however, that this arrangement of teeth may expose a rough outer surface even when the jaws are closed during their entry into and exit from the lumen of the endoscope. It is believed that the perceived rough outer surface of the closed jaws might cause damage or undue wear to the lumen of the endoscope.